The present invention is related to an improved caster structure having better connection strength for more stably support an appliance, whereby the appliance can be more freely moved and rotated.
FIG. 6 shows a conventional caster having a seat body 81 mounted under the bottom of an appliance. The seat body 81 has a fixing hole 811 for a fixing section 821 of a thread rod 82 to pass therethrough and be riveted and fixed. An upper bearing cover 83, a caster seat 84 and a lower bearing cover 85 are fitted on the bottom end of the thread rod 82. Multiple beads 86 are disposed between the upper bearing cover 83, caster seat 84 and lower bearing cover 85 to form a thrust bearing. A nut 87 is screwed on the rear end of the thread rod 82 to fix the same. A wheel 841 is rotatably connected with the caster seat 84.
Referring to FIG. 7, when moving the appliance, the total weight of the appliance is loaded onto the caster 841. Accordingly, the thread rod 82, caster seat 84 and the upper and lower bearing covers 83, 85 all suffer considerably great stress in different directions. After a period of use, the thread rod 82 is simply riveted with the seat body 81 and is not restricted from rotation. Therefore, when suffering the force, the fixing section 821 of the thread rod 82 will rotate and swing within the fixing hole 811 of the seat body 81 to enlarge the fixing hole 811. Also, the rivet section of the fixing section 821 will be worn out and deformed. As a result, the thread rod 82 will swing to affect the stability of the appliance and the caster no more simply suffers axial force from the appliance. Accordingly, the caster seat 84 will be seriously tilted and when pushing the appliance, a corner of the appliance may suddenly lose the support to lead to unbalance of the appliance. Under such circumstance, the appliance may fall down and cause danger. Furthermore, moving the appliance, the upper bearing cover 83 will suffer force in different directions to gradually enlarge the hole 831 in which the thread rod 82 is fitted. Also, the upper bearing cover 83 will bend, deform and loosen. Accordingly, the gap between the circumference 832 of the upper bearing cover 83 and the caster seat 84 will be enlarged and the bead 86 may drop out and lose the effect of the thrust bearing. As a result, it will be hard to rotate and change the direction of the caster seat 84.
It is therefore a primary object of the present invention to provide an improved caster structure in which the seat body is formed with a differential fixing hole and the top of the linking member is formed with a fixing section. The shape of the cross-section of the fixing section is an internal tangential circle of the differential fixing hole. When the fixing section is passed through the fixing hole and compressed and fixedly riveted, the fixing section will form a differential section complementary to the fixing hole. Accordingly, the linking member is firmly connected with the seat body without rotation. Therefore, the linking member and the seat body are prevented from being worn out and deformed and the problem caused by tilting of the linking member can be avoided and the appliance can be stably moved.
It is a further object of the present invention to provide the above caster structure in which the upper bearing cover is integrally formed with the linking member so that the upper bearing cover is not subject to wearing and deformation. The bearing section of the caster seat is formed with an annular rib corresponding to the outer circumference of the upper bearing cover for stopping the beads from dropping out. Therefore, the thrust bearing effect can be kept and the caster seat can be freely moved to change the direction of the wheel.
The present invention can be best understood through the following description and accompanying drawings wherein: